1. Field of Invention
The invention relates to a multilayer structure and, in particular, to a multilayer structure with diamond-like carbon.
2. Related Art
The current fingerprint identification device can be divided into an optical type and a non-optical type. The optical type of fingerprint identification device is more expensive and highly consumptive of the power (for the light source) and has a larger size (caused by the required distance for the optical imaging and the dimensions of the optical components), so that it's unsuitable for the application of portable electronic products such as notebooks and mobile phones.
The non-optical type of fingerprint identification device includes an electronic fingerprint identification device, an electrostatic induction fingerprint identification device, a capacitive sensing fingerprint identification device, and a thermal sensing fingerprint identification device. The electronic fingerprint identification device also has the problem of high power consumption (the sensing elements thereof will have a current flow during the contact of the two electrodes) and is uneasy to be integrated with the integrated circuit (the manufacturing of piezoelectric material is not compatible for the IC process). The electrostatic induction fingerprint identification device and the capacitive sensing fingerprint identification device are easily affected by dust, sweat on fingers and electromagnetic interference, and a complicated analog circuit is required to read out the tiny electric signal of the sensing element. In manufacturing, although the electrostatic induction fingerprint identification device and the capacitive sensing fingerprint identification device are compatible for the IC process, the high-level IC process is required to result in a better process result, and the cost is increased therefore. Accordingly, the thermal sensing fingerprint identification device is a better option for the application of portable electronic products.
The thermal sensing fingerprint identification device basically includes a heating resistor, a sensing electrode and a temperature sensor. In the thermal sensing fingerprint identification device, the temperature of the sensing electrode is raised by the heating resistor to be over the human temperature and then lowered by the finger contacting the sensing electrode to take some heat away. Then, the thermal sensing fingerprint identification device can obtain a temperature image corresponding to the fingerprint through the temperature sensor.
However, the sensing electrode is easy to be damaged because the user needs to always contact the sensing electrode, and thus the thermal sensing fingerprint identification device will fail in the operation. Moreover, since the user contacts the electrode directly by the finger, the current leakage of the thermal sensing fingerprint identification device may flow to the user's finger through the sensing electrode so that the user may get an electric shock. Besides, the user may receive some toxic substances of the thermal sensing fingerprint identification device through the sensing electrode. Therefore, it is an important subject to protect the sensing electrode from being damaged and let the user safely use the thermal sensing fingerprint identification device.